For Immediate Release: August 21, 2026

Harmful algal blooms (HABs) persist on different areas of Hebgen Reservoir. Currently, the toxin levels at Corey Springs area have increased, and that area is now closed for water-based activities because toxin levels are high. Closure signs will be posted at public access points in the Corey Springs area warning the public that toxic algae has been identified in the water, and that the area is closed to water-based activities.  

The Rainbow Point shoreline also remains closed due to high toxin levels during regular sampling. The Yellowstone Holiday area toxins have dissipated, and it has been downgraded to a warning. Caution is still strongly encouraged wherever toxic algae is present.    

Read the full press release here. 

When in doubt, stay out! You can’t tell for sure if an algal or cyanobacterial bloom is harmful just by looking at it. Protect yourself, your family, and your pets by not swimming in bodies of water that smell bad or look discolored. Children and pets are more likely to ingest HAB infested water because they spend most of their time wading in the shallow waters where algae can accumulate and they have less control over how much water they ingest.